Chris's Corner - Conditional Risk for Isolated Severe Storms

[Chris Higgins]

***A SNEAKY AND VERY CONDITIONAL THREAT FOR SEVERE WEATHER LATE SATURDAY***
***WORK CONTINUES TO PREP FOR BRINGING MTW BEHIND A PRIVACY WALL***

We really needed this new thread…and this seems like the right time. It’s a new month and the pattern is going into flux-mode with some really crazy and chaotic motions in the upper-level pattern forecast over the next week to ten days.

Let’s start with Saturday…
There are some pretty healthy parameters that would support severe storms with all modes of severe for Saturday afternoon. Instability, lapse rates, dew points, wind shear. There is one healthy limiting factor in the form of a sizeable, but not insurmountable capping inversion. And then there is the overall wishy-washy forcing mechanism… both near surface and aloft. I think the key to a trigger may end up being morning showers leaving behind a remnant discontinuity of some sort… an outflow boundary/minor cool pool/slightly backed surface winds. The HRRR shows the potential as you can see with this somewhat cherry-picked hodograph near the time it blows-up two supercells just west of STL. So the development of something in the AM may be key to providing a trigger or focus for isolated intense storms in the afternoon. If morning showers do not materialize along the warm-front then the cap likely winds the day in my opinion. That’s a lot of iffs and maybes… and given the other favorable parameters… I don’t have a problem with SPC hoisting the SLIGHT risk. In short, I have low confidence in storm development. However, if storms do develop, I have moderate confidence in them becoming severe with all manner of severe weather possible.

No matter what happens, it would seem that our temperatures are heading upwards…and if rain/storm coverage is limited to non-existent… then temperatures will really skyrocket.

As for going behind the privacy wall… I know I’ve said this before…it is coming…but I need more time. I will post another new thread for a few days before the switch so everyone knows it’s coming.

[bellevillewxguy]

Do think we'll get our first 90*F day under our belts for the metro area Sunday or Monday depending on clouds and precip. This week coming up is gonna feel like a heat wave in comparison to what we have been dealing with and a good reminder to get your ACs checked and finally put away the winter clothes, hopefully once and for all for the season!

[John G -west belleville]

Who has the ecowitt weather station? Going to bite the bullet and install a complete weather station on the house.

[Chris Higgins]

In case you haven't heard... the Euro is getting a big update this summer.

www.meteorologicaltechnologyinternational.com/news/climate-measurement/ecmwf-updates-integrated-forecasting-system.html

[Labrat-O'Fallon IL]

Full moon from my deck. Love the fact I work from home and can enjoy this.

[guyatacomputer - NE St. Peters]

Should they develop what is time frame for any storms on Saturday?

[bellevillewxguy]

May 5, 2023 20:07:32 GMT -6 guyatacomputer - NE St. Peters said:

Should they develop what is time frame for any storms on Saturday?

Small but conditional chance Saturday AM before 10AM and again After 4PM.

Some models are going quite bonkers around 7-10AM particularly the 3KM NAM, while others show nothing more then a few showers if anything. Sunday seems to be better, but again not a ton of agreement amongst the models.

[Snowstorm920]

Just alittle bit of instability around here Monday on the NAM

It has a beefy MCS moving through this environment

[bellevillewxguy]

SPC blew up the risk today to the north of I-70 with slight risk now covering much of north/central MO and Central/Northern Illinois with the metro on the edge. Looks like showers and storms are expanding in coverage to the north and west of the metro.

[REB]

Just got home from a trip to Spain. They are in a drought but the temps were wonderful. I would love to see some rain here but not the 90's. Enjoy your weekend friends.

[amstilost]

Just had a quick shower from the pop up just coming into southern JeffCo. I am hoping for more but it just might be a tad south for me.

[BRTNWXMAN]

NAM looking stout with an MCS impacting the region tomorrow morning with genesis across N MO/S IA tonight. Definitely a healthy plume of instability to work with...that'll need to be watched for severe wind potential with 40-50kts of NWerly shear.

[Lovableweatherguy TROY,MO]

Severe cluster up near Hannibal is starting to turn more east southeast. Could effect the western viewing area...

[John G -west belleville]

The rest of the day is going to hinge on where that outflow sets up

[BRTNWXMAN]

May 6, 2023 10:22:25 GMT -6 John G -west belleville said:

The rest of the day is going to hinge on where that outflow sets up

9

Quite a bit of agitated/towering CU just west of the Metro ahead of it. Storms are trying to get going.

[amstilost]

I have more pop up's just to the north of me now, 7 miles west of De Soto. Cloudy up quite a bit too.

[Snowstorm920]

That cluster to our north is sending out a well defined outflow boundary

Going to have to watch that for re development this afternoon

[BRTNWXMAN]

May 6, 2023 11:25:40 GMT -6 Snowstorm920 said:

That cluster to our north is sending out a well defined outflow boundary

Going to have to watch that for re development this afternoon

Radar showing some weak returns down near Cuba...looks like some WAA/Mcon is occurring over the boundary that could get more storms going later this afternoon.

[Spaz(Wrestlerdude)]

We still expecting another wave today?

[tedrick65]

Speaking of waves... Interesting radar look

[STGOutdoors]

I noticed that too. I guess that’s dust blowing in the southern wind?

[Snowstorm920]

“Horizontal convective rolls are counter-rotating horizontal circulations within the boundary layer and are often a precursor to convective development. They usually appear on radar on mostly clear days with strong surface heating and a fairly steady wind direction. Insects and other particulates act as tracers of the roll circulations before clouds form, and birds are often present in these areas to feed on the concentrated insects.”


kejian1.cmatc.cn/vod/comet/radar/basic_wxradar/navmenu.php_tab_1_page_5.2.2_type_text.htm

[Snowstorm920]

Latest HRRR takes the storm in NW MO and forms an MCS that tries to track down the river tonight

[BRTNWXMAN]

May 6, 2023 17:17:53 GMT -6 Snowstorm920 said:

Latest HRRR takes the storm in NW MO and forms an MCS that tries to track down the river tonight

Looks similar to the 12z NAMs but a much earlier arrival. Definitely a good setup for a S/SE propagating MCS with ~40kt W/NW mid-level flow and the LLJ nosing into N MO and then veering out overnight.

[Snowstorm920]

Box sounding ahead of the line this evening is impressive

[BRTNWXMAN]

Big time DCAPE

[STGOutdoors]

Damn, grapefruit size hail report on mping on NWMO. Strong wording on the warning too -“THIS IS A DESTRUCTIVE STORM.”

[Labrat-O'Fallon IL]

Is there anyone on here handy and can put in a dog door? We have the hole in the wall, but my husband is having issues screwing it in.

[Chris Higgins]

May 6, 2023 17:55:08 GMT -6 BRTNWXMAN said:

Big time DCAPE

Yeah, that has my attention.
It is always a bit of a mystery sorting out how these types of events play out... But i'm getting more concerned by the minute about a high wind event evolving late tonight.

[bellevillewxguy]

Well from the looks of Radarscope it seems the massive supercell has begun the southeastern turn. Doesn't seem to be expanding or propagating just yet though. Is a LLJ supposed to get involved at all? If so then we might see some action expand later this evening into the overnight.